Within each group, the teams would play a double round-robin to decide their league position.
The four third-last placed teams would compete a play-out against the ninth relegation spot.
The decider was played on 21 May in Montreux FC Châtel-Saint-Denis win and advance to play-offs.
Liga Interregional The decider was played on 21 May 1991 at the Stadion Schlottermilch in Sursee FC Pratteln win and advance to play-offs.
The decider was played on 21 May in Altstetten (Zürich) SC Veltheim win and advance to play-outs.
Liga Interregional FC Brüttisellen win 3–2 on aggregate and continue to the finals.